1. Field of the Invention
The invention relates in general to a method for grinding lens, and more particularly to a method for grinding lens without mechanic contact.
2. Description of the Related Art
Of today's laser processing technology, gas laser has been widely used in drilling, cutting, engraving, welding, material heat treatment, and so on. In the technology of gas laser, gas is used as an active medium and is sealed inside a resonant cavity. The resonant cavity consists of two pieces of lens: the front one is a semi-reflecting lens while the rear one is a total-reflecting lens. Each of the two lenses has an optical surface and a gas contact surface, wherein the gas contact surface contacts with the gas which is sealed inside the resonant cavity. The operation of gas laser is that when a voltage or a current passes through an optical resonant cavity, the gas will be excited to create a monochromatic narrow light-beam of high homology which can be focused on a tiny spot with great precision for laser processing. The oscillation frequency of the laser light has much to do with the penetration rate of the lens used in the resonant cavity, i.e., the lower the penetration rate, the higher the oscillation frequency.
It is noteworthy that after a period of gas laser operation some blemishes or spots which severely affect lens quality will be formed on the gas contact surface of the lens, so the lens needs to be replaced after a certain period of operation. Since the lens used in gas laser is very expensive, lens replacement is a big expenditure for gas laser operation. As shown in FIG. 1, since optical surface 13 of lens 12 is so sensitive that an operator cannot use any mechanic tool for polishing pad 15 to grind surface-to-be-grinded 14, the other side of lens corresponding to optical surface 13. Even if force is applied from the lateral side of the lens, the conventional grinding method with mechanic contact still cannot apply the force evenly to achieve an even grinding. That is to say, when polishing pad 15 moves along with the direction of arrow 50 in FIG. 1, surface-to-be-grinded 14 will not be able to move in parallel to polishing pad 15 due to the force coming from the lateral side of lens 12. Particularly, the higher the level of evenness required is, the poorer the result of the above method will be.